Estrogen Receptor and Progesterone Receptor Positive Pigmented Extramammary Paget’s Disease of the Axilla Mimicking Melanoma: A Case Report and Review of the Literature

Pigmented extramammary Paget’s disease (EMPD) is a rare variant which is often confused clinically and histologically with melanoma or other pigmented lesions. Herein, we describe a rare case of pigmented EMPD involving the axilla of a 40-year-old female thought initially to represent malignant melanoma clinically. Immunohistochemically, the neoplastic cells are positive for Estrogen Receptor (ER), Progesterone Receptor (PR), and weakly positive for Human Epidermal Growth Factor Receptor 2 (Her2). A review of the literature reveals that the pigmented variant of EMPD could be easily misdiagnosed as melanoma initially and additional confirmatory studies are almost always needed to confirm the diagnosis. The expression of ER and PR in pigmented EMPD is rarely mentioned previously. We believe it should be further investigated for the understanding of pathogenesis in pigmented EMPD and the potential role of adjuvant hormonal therapy. Keywords: Extramammary Paget’s Disease; Axilla; Estrogen Receptor; Progesterone Receptor